Peptide 19 of Porphyromonas gingivalis Heat Shock Protein Is a Potent Inducer of Low-Density Lipoprotein Oxidation.

BACKGROUND: Although periodontal pathogens show a strong association with development of atherosclerosis, little is known about how a microorganism contributes to disease onset and progression. Oxidation of low-density lipoprotein (LDL) is a major risk factor of atherogenesis. The principal objective of this study is to evaluate the ability of peptide 19 (Pep19) of Porphyromonas gingivalis (Pg) heat shock protein (HSP) as a potent inducer of LDL oxidation, and a secondary objective is to compare this ability with that of Pep19 from different bacteria.

METHODS: HSP60, Pep14, and Pep19 from Pg and THP-1 monocytes were cultured, and the extent of LDL oxidation induced by each peptide was evaluated by an assay for thiobarbituric acid-reactive substances (TBARS). Pep19 and HSP60 from Chlamydia pneumoniae and Mycobacterium tuberculosis were also cultured with THP-1 monocytes and evaluated by the TBARS assay. After incubation of macrophages with LDL and peptides from Pg, Oil Red O staining was performed for examination of foam cells, macrophages that took up the oxidized LDL.

RESULTS: Monocyte-mediated native-LDL oxidation under the influence of Pep19 or HSP60 from Pg was significantly stronger than oxidation induced by the counterpart Pep19 or HSP60 from C. pneumoniae or M. tuberculosis. Pep19 from Pg HSP60 showed a stronger ability to induce LDL oxidation than did Pep14 from Pg HSP60.

CONCLUSION: These results suggest Pep19 from Pg HSP60 has a distinct ability to induce native-LDL oxidation as a plausible mechanism by which this peptide may drive epitope spreading to the neoantigen, i.e., oxidized LDL, in the pathogenesis of atherosclerosis.